![Thomas Gleixner](/assets/img/avatar_default.png)
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public licence as published by the free software foundation either version 2 of the licence or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 114 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190520170857.552531963@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
465 lines
12 KiB
C
465 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Verify the signature on a PKCS#7 message.
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define pr_fmt(fmt) "PKCS7: "fmt
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/slab.h>
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#include <linux/err.h>
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#include <linux/asn1.h>
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#include <crypto/hash.h>
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#include <crypto/public_key.h>
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#include "pkcs7_parser.h"
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/*
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* Digest the relevant parts of the PKCS#7 data
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*/
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static int pkcs7_digest(struct pkcs7_message *pkcs7,
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struct pkcs7_signed_info *sinfo)
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{
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struct public_key_signature *sig = sinfo->sig;
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struct crypto_shash *tfm;
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struct shash_desc *desc;
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size_t desc_size;
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int ret;
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kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo);
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if (!sinfo->sig->hash_algo)
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return -ENOPKG;
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/* Allocate the hashing algorithm we're going to need and find out how
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* big the hash operational data will be.
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*/
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tfm = crypto_alloc_shash(sinfo->sig->hash_algo, 0, 0);
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if (IS_ERR(tfm))
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return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
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desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
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sig->digest_size = crypto_shash_digestsize(tfm);
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ret = -ENOMEM;
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sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
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if (!sig->digest)
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goto error_no_desc;
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desc = kzalloc(desc_size, GFP_KERNEL);
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if (!desc)
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goto error_no_desc;
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desc->tfm = tfm;
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/* Digest the message [RFC2315 9.3] */
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ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len,
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sig->digest);
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if (ret < 0)
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goto error;
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pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest);
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/* However, if there are authenticated attributes, there must be a
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* message digest attribute amongst them which corresponds to the
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* digest we just calculated.
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*/
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if (sinfo->authattrs) {
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u8 tag;
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if (!sinfo->msgdigest) {
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pr_warn("Sig %u: No messageDigest\n", sinfo->index);
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ret = -EKEYREJECTED;
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goto error;
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}
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if (sinfo->msgdigest_len != sig->digest_size) {
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pr_debug("Sig %u: Invalid digest size (%u)\n",
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sinfo->index, sinfo->msgdigest_len);
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ret = -EBADMSG;
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goto error;
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}
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if (memcmp(sig->digest, sinfo->msgdigest,
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sinfo->msgdigest_len) != 0) {
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pr_debug("Sig %u: Message digest doesn't match\n",
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sinfo->index);
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ret = -EKEYREJECTED;
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goto error;
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}
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/* We then calculate anew, using the authenticated attributes
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* as the contents of the digest instead. Note that we need to
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* convert the attributes from a CONT.0 into a SET before we
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* hash it.
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*/
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memset(sig->digest, 0, sig->digest_size);
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ret = crypto_shash_init(desc);
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if (ret < 0)
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goto error;
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tag = ASN1_CONS_BIT | ASN1_SET;
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ret = crypto_shash_update(desc, &tag, 1);
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if (ret < 0)
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goto error;
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ret = crypto_shash_finup(desc, sinfo->authattrs,
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sinfo->authattrs_len, sig->digest);
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if (ret < 0)
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goto error;
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pr_devel("AADigest = [%*ph]\n", 8, sig->digest);
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}
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error:
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kfree(desc);
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error_no_desc:
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crypto_free_shash(tfm);
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kleave(" = %d", ret);
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return ret;
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}
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/*
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* Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
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* uses the issuer's name and the issuing certificate serial number for
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* matching purposes. These must match the certificate issuer's name (not
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* subject's name) and the certificate serial number [RFC 2315 6.7].
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*/
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static int pkcs7_find_key(struct pkcs7_message *pkcs7,
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struct pkcs7_signed_info *sinfo)
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{
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struct x509_certificate *x509;
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unsigned certix = 1;
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kenter("%u", sinfo->index);
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for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
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/* I'm _assuming_ that the generator of the PKCS#7 message will
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* encode the fields from the X.509 cert in the same way in the
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* PKCS#7 message - but I can't be 100% sure of that. It's
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* possible this will need element-by-element comparison.
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*/
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if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0]))
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continue;
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pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
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sinfo->index, certix);
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if (strcmp(x509->pub->pkey_algo, sinfo->sig->pkey_algo) != 0) {
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pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
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sinfo->index);
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continue;
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}
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sinfo->signer = x509;
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return 0;
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}
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/* The relevant X.509 cert isn't found here, but it might be found in
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* the trust keyring.
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*/
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pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
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sinfo->index,
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sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data);
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return 0;
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}
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/*
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* Verify the internal certificate chain as best we can.
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*/
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static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
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struct pkcs7_signed_info *sinfo)
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{
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struct public_key_signature *sig;
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struct x509_certificate *x509 = sinfo->signer, *p;
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struct asymmetric_key_id *auth;
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int ret;
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kenter("");
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for (p = pkcs7->certs; p; p = p->next)
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p->seen = false;
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for (;;) {
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pr_debug("verify %s: %*phN\n",
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x509->subject,
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x509->raw_serial_size, x509->raw_serial);
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x509->seen = true;
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if (x509->blacklisted) {
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/* If this cert is blacklisted, then mark everything
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* that depends on this as blacklisted too.
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*/
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sinfo->blacklisted = true;
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for (p = sinfo->signer; p != x509; p = p->signer)
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p->blacklisted = true;
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pr_debug("- blacklisted\n");
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return 0;
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}
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if (x509->unsupported_key)
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goto unsupported_crypto_in_x509;
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pr_debug("- issuer %s\n", x509->issuer);
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sig = x509->sig;
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if (sig->auth_ids[0])
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pr_debug("- authkeyid.id %*phN\n",
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sig->auth_ids[0]->len, sig->auth_ids[0]->data);
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if (sig->auth_ids[1])
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pr_debug("- authkeyid.skid %*phN\n",
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sig->auth_ids[1]->len, sig->auth_ids[1]->data);
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if (x509->self_signed) {
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/* If there's no authority certificate specified, then
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* the certificate must be self-signed and is the root
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* of the chain. Likewise if the cert is its own
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* authority.
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*/
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if (x509->unsupported_sig)
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goto unsupported_crypto_in_x509;
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x509->signer = x509;
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pr_debug("- self-signed\n");
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return 0;
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}
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/* Look through the X.509 certificates in the PKCS#7 message's
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* list to see if the next one is there.
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*/
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auth = sig->auth_ids[0];
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if (auth) {
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pr_debug("- want %*phN\n", auth->len, auth->data);
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for (p = pkcs7->certs; p; p = p->next) {
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pr_debug("- cmp [%u] %*phN\n",
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p->index, p->id->len, p->id->data);
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if (asymmetric_key_id_same(p->id, auth))
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goto found_issuer_check_skid;
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}
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} else if (sig->auth_ids[1]) {
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auth = sig->auth_ids[1];
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pr_debug("- want %*phN\n", auth->len, auth->data);
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for (p = pkcs7->certs; p; p = p->next) {
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if (!p->skid)
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continue;
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pr_debug("- cmp [%u] %*phN\n",
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p->index, p->skid->len, p->skid->data);
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if (asymmetric_key_id_same(p->skid, auth))
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goto found_issuer;
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}
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}
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/* We didn't find the root of this chain */
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pr_debug("- top\n");
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return 0;
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found_issuer_check_skid:
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/* We matched issuer + serialNumber, but if there's an
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* authKeyId.keyId, that must match the CA subjKeyId also.
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*/
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if (sig->auth_ids[1] &&
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!asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
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pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
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sinfo->index, x509->index, p->index);
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return -EKEYREJECTED;
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}
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found_issuer:
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pr_debug("- subject %s\n", p->subject);
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if (p->seen) {
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pr_warn("Sig %u: X.509 chain contains loop\n",
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sinfo->index);
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return 0;
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}
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ret = public_key_verify_signature(p->pub, x509->sig);
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if (ret < 0)
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return ret;
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x509->signer = p;
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if (x509 == p) {
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pr_debug("- self-signed\n");
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return 0;
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}
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x509 = p;
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might_sleep();
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}
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unsupported_crypto_in_x509:
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/* Just prune the certificate chain at this point if we lack some
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* crypto module to go further. Note, however, we don't want to set
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* sinfo->unsupported_crypto as the signed info block may still be
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* validatable against an X.509 cert lower in the chain that we have a
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* trusted copy of.
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*/
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return 0;
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}
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/*
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* Verify one signed information block from a PKCS#7 message.
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*/
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static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
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struct pkcs7_signed_info *sinfo)
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{
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int ret;
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kenter(",%u", sinfo->index);
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/* First of all, digest the data in the PKCS#7 message and the
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* signed information block
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*/
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ret = pkcs7_digest(pkcs7, sinfo);
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if (ret < 0)
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return ret;
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/* Find the key for the signature if there is one */
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ret = pkcs7_find_key(pkcs7, sinfo);
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if (ret < 0)
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return ret;
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if (!sinfo->signer)
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return 0;
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pr_devel("Using X.509[%u] for sig %u\n",
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sinfo->signer->index, sinfo->index);
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/* Check that the PKCS#7 signing time is valid according to the X.509
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* certificate. We can't, however, check against the system clock
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* since that may not have been set yet and may be wrong.
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*/
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if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
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if (sinfo->signing_time < sinfo->signer->valid_from ||
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sinfo->signing_time > sinfo->signer->valid_to) {
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pr_warn("Message signed outside of X.509 validity window\n");
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return -EKEYREJECTED;
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}
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}
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/* Verify the PKCS#7 binary against the key */
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ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig);
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if (ret < 0)
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return ret;
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pr_devel("Verified signature %u\n", sinfo->index);
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/* Verify the internal certificate chain */
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return pkcs7_verify_sig_chain(pkcs7, sinfo);
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}
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/**
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* pkcs7_verify - Verify a PKCS#7 message
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* @pkcs7: The PKCS#7 message to be verified
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* @usage: The use to which the key is being put
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*
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* Verify a PKCS#7 message is internally consistent - that is, the data digest
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* matches the digest in the AuthAttrs and any signature in the message or one
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* of the X.509 certificates it carries that matches another X.509 cert in the
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* message can be verified.
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*
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* This does not look to match the contents of the PKCS#7 message against any
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* external public keys.
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*
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* Returns, in order of descending priority:
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*
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* (*) -EKEYREJECTED if a key was selected that had a usage restriction at
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* odds with the specified usage, or:
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*
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* (*) -EKEYREJECTED if a signature failed to match for which we found an
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* appropriate X.509 certificate, or:
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*
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* (*) -EBADMSG if some part of the message was invalid, or:
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*
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* (*) 0 if a signature chain passed verification, or:
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*
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* (*) -EKEYREJECTED if a blacklisted key was encountered, or:
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*
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* (*) -ENOPKG if none of the signature chains are verifiable because suitable
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* crypto modules couldn't be found.
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*/
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int pkcs7_verify(struct pkcs7_message *pkcs7,
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enum key_being_used_for usage)
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{
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struct pkcs7_signed_info *sinfo;
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int actual_ret = -ENOPKG;
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int ret;
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kenter("");
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switch (usage) {
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case VERIFYING_MODULE_SIGNATURE:
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if (pkcs7->data_type != OID_data) {
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pr_warn("Invalid module sig (not pkcs7-data)\n");
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return -EKEYREJECTED;
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}
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if (pkcs7->have_authattrs) {
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pr_warn("Invalid module sig (has authattrs)\n");
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return -EKEYREJECTED;
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}
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break;
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case VERIFYING_FIRMWARE_SIGNATURE:
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if (pkcs7->data_type != OID_data) {
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pr_warn("Invalid firmware sig (not pkcs7-data)\n");
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return -EKEYREJECTED;
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}
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if (!pkcs7->have_authattrs) {
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pr_warn("Invalid firmware sig (missing authattrs)\n");
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return -EKEYREJECTED;
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}
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break;
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case VERIFYING_KEXEC_PE_SIGNATURE:
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if (pkcs7->data_type != OID_msIndirectData) {
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pr_warn("Invalid kexec sig (not Authenticode)\n");
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return -EKEYREJECTED;
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}
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/* Authattr presence checked in parser */
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break;
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case VERIFYING_UNSPECIFIED_SIGNATURE:
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if (pkcs7->data_type != OID_data) {
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pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
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return -EKEYREJECTED;
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}
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break;
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default:
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return -EINVAL;
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}
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for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
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ret = pkcs7_verify_one(pkcs7, sinfo);
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if (sinfo->blacklisted) {
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if (actual_ret == -ENOPKG)
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actual_ret = -EKEYREJECTED;
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continue;
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}
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if (ret < 0) {
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if (ret == -ENOPKG) {
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sinfo->unsupported_crypto = true;
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continue;
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}
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kleave(" = %d", ret);
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return ret;
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}
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actual_ret = 0;
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}
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kleave(" = %d", actual_ret);
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return actual_ret;
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}
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EXPORT_SYMBOL_GPL(pkcs7_verify);
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/**
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* pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
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* @pkcs7: The PKCS#7 message
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* @data: The data to be verified
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* @datalen: The amount of data
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*
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* Supply the detached data needed to verify a PKCS#7 message. Note that no
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* attempt to retain/pin the data is made. That is left to the caller. The
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* data will not be modified by pkcs7_verify() and will not be freed when the
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* PKCS#7 message is freed.
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*
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* Returns -EINVAL if data is already supplied in the message, 0 otherwise.
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*/
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int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
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const void *data, size_t datalen)
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{
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if (pkcs7->data) {
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pr_debug("Data already supplied\n");
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return -EINVAL;
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}
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pkcs7->data = data;
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pkcs7->data_len = datalen;
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return 0;
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}
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